mirror of
https://github.com/FirebirdSQL/firebird.git
synced 2025-01-22 21:23:04 +01:00
39 lines
1.2 KiB
Plaintext
39 lines
1.2 KiB
Plaintext
============================
|
|
Regular expression SUBSTRING
|
|
============================
|
|
|
|
Function:
|
|
|
|
Regular expression SUBSTRING returns the portion of a value who matches a SIMILAR pattern. If the
|
|
match does not occur, it returns NULL.
|
|
|
|
Author:
|
|
Adriano dos Santos Fernandes <adrianosf at gmail.com>
|
|
|
|
|
|
Syntax:
|
|
|
|
<regular expression substring> ::=
|
|
SUBSTRING(<value> FROM <similar pattern> ESCAPE <escape character>)
|
|
|
|
<similar pattern> ::= <character value expression: substring similar expression>
|
|
|
|
<substring similar expression> ::=
|
|
<similar pattern: R1><escape>"<similar pattern: R2><escape>"<similar pattern: R3>
|
|
|
|
|
|
Notes:
|
|
1) If any one of R1, R2, or R3 is not a zero-length string and does not have the format of a
|
|
<similar pattern>, then an exception is raised.
|
|
2) The returned value is the matching portion of R2 where
|
|
<value> SIMILAR TO R1 || R2 || R3 ESCAPE <escape>
|
|
|
|
|
|
Examples:
|
|
|
|
substring('abcabc' similar 'a#"bcab#"c' escape '#') -- bcab
|
|
substring('abcabc' similar 'a#"%#"c' escape '#') -- bcab
|
|
substring('abcabc' similar '_#"%#"_' escape '#') -- bcab
|
|
substring('abcabc' similar '#"(abc)*#"' escape '#') -- abcabc
|
|
substring('abcabc' similar '#"abc#"' escape '#') -- <null>
|